Like the best portrait painters, Tom Zetterstrom draws forth the sap and heartwood of the trees he's photographed for 35 years.

In gorgeous black-and-white images, he captures not just the natural grandeur of trees but their power to evoke deep yearnings in human viewers.

The Canaan, Conn., photographer's just-opened exhibit, "Tom Zetterstrom: Portraits of American Trees," transforms the Cantor Gallery at the College of the Holy Cross into a forest of photos where visitors can walk among maples and red pines, poplars and shagbark hickories.

Part arborist, part impressionist with a camera, Zetterstrom has made portraits of trees that -- like Gilbert Stuart's "Portrait of George Washington" or Andrew Wyeth's "Cristina's World" -- reveal much more than their physical likenesses.

Zetterstrom said he began photographing trees after college when he was living in a cabin with a basement darkroom in the woods on his family property in Canaan.

"I think I was really looking at them as art. I guess I've got a lot of feelings about trees, a passion," he said from his home. "My work in the show aren't so much documentary photos as interpretive images."

The exhibit runs through Oct. 9.

In a catalog accompanying the exhibit, John Elder, professor emeritus of English and environmental studies at Middlebury College, wrote, "Zetterstrom's photography expresses a parallel sense of deep affiliation with the beautiful, transient and memorable lives of trees."

Describing a storm-whipped pine at Donner Pass in California, he wrote the tree's endurance illustrates the central point of William Wordsworth's "Ode: Intimations of Immortality" that "A single, vividly observed natural fact can assume almost mythic power, enduring for the whole of an observer's life."

Through craft and conviction, Zetterstrom imbues trees with the kind of inner life that primitive people ascribe to natural phenomena like stones, animals or mountains.

Most of the 60 photos depict solitary trees as living -- sometimes dying -- natural objects or tightly focused scenes which, like a mirror, reflect human emotions and associations.

The trees in these photos will stir viewers' memories. New Englanders might recall Henry David Thoreau's "Walden" began "I went to the woods because I wished to live deliberately." Worcester residents can't forget the Asian longhorn beetles last year that devastated sugar maples in the city.

Students at the Catholic college should know Dante began his "Divine Comedy" saying: "Midway upon the road of life I found myself in a dark wood because the right way had been lost." And where did Little Red Riding Hood meet the Big Bad Wolf? Zetterstrom's woods are haunted, enchanted and full of surprises.

Entering the gallery, visitors will see an American elm in wintertime, spreading leafless branches against a gray sky.

Page 2 of 3 - There are no people in these photos but their impact can be inferred from the jumble of burnt trees in the Sawtooth Mountains of Colorado.

These trees bend in the wind and cast reflections on rushing rivers. Their branches droop beneath the weight of snow or point like skeletal fingers into the sky.

Mostly alone, they sometimes lean against each other for support, stand apart like feuding twins or stick out of the ground, bare and dead like dinosaur bones.

A yellow birch takes root on a stony ledge with branches spreading like tendrils onto sheer rock. Like an old couple, the gnarled trunks of a maple and cherry tree have grown together. Dead or dying, the white branches of two northern white cedars rise like wraiths from a Maine river.

Taken between 1973 and 2006, the mostly 5 1/2-by-7 1/2-inch photos are displayed against white matting that gives the impression of looking through a cabin window.

The exhibit's organizer, Gallery Director Roger Hankins, said he "avoided theatrical contrasts" and showed the photos against a neutral background so they'd stand out "like little jewels."

He speculated Zetterstrom printed modestly sized photos to encourage visitors "to get up close and personal, like they're viewing a portrait."

"It's like the trees in these photos are almost detached from culture and exist in another world," Hankins said. "Tom (Zetterstrom) wanted them shown in a way visitors could meditate on them."

Hankins believes Zetterstrom's longterm efforts taking and printing tree photos demonstrates his conviction as an environmental activist who has used his art to protect endangered natural resources. Zetterstrom founded Elm Watch, a regional community forestry organization, he said.

Hankins organized the exhibit into 15 groupings of three to five photos that suggest unstated themes such as misty images, desolate places, Canadian scenes, spruce trees and the virtual disappearance of American elms from Dutch elm disease.

In a series of four photos taken in Massachusetts between 1993 and 1997, an elm tree gradually loses leaves from its withering branches until the final shot where it stands alone, nearly denuded, in a field.

One remarkable grouping of five dramatic photos expresses nature's irresistible drive to survive. Pictured from below, a cobble hemlock soars skyward, its spreading branches blotting out the sky. The long limbs of a shagbark hickory twist in improbable ways. Branches hang from a weeping beech like tangled black capillaries.

Growing on rock, a yellow birch converts its branches into roots. White cedars die in a river.

The son of an arborist, Zetterstrom studied botany and sculpture at Colorado College and photography at Pratt Institute. He worked as a freelance photojournalist in the 1970s and '80s with assignments ranging from the New York Times to "A Day in the Life of America." He's worked in Russia and China and his photos can be found in the collections of 37 American museums.

Page 3 of 3 - Zetterstrom said the exhibit is "foremost an art show but inadvertently and intentionally a message about the environment comes through."

He used a 35 mm camera throughout the 1970s and switched in 1983 to a medium format Fujica that used larger negatives to capture subtle gradations of color and light.

Zetterstrom said he "tries, ultimately, to make art" from his tree photos but realizes viewers personalize them in different ways. He said he "feels reverential toward trees as a life force."

"Foremost, I respect trees as the record of great lives. Whether they're 100, 500 or 4,000 years old, you can read all sorts of things into them," he said. "For some people, trees have spiritual connotations. Many people have lingering associations about trees. Through my photos, I'm trying to amplify that into an appreciation of trees."

For 35 years, Zetterstrom has traveled across North America hiking into forests or driving to remote spots to find the special tree.

"I do a lot of exploring. I've looked at millions of trees," he said. "Occasionally, I come across something hidden, startling or remarkable."

THE ESSENTIALS

Cantor Gallery is on the first floor of O'Kane Hall at College of the Holy Cross in Worcester.

The gallery is open 10 a.m. to 5 p.m. Monday to Friday and 2 to 5 p.m. Saturday. Admission is free.

Tom Zetterstrom will appear at a Thursday, Sept. 16, reception from 4:30 to 6:30 p.m. He'll lecture on his work at 7:30 p.m. in the college's Seelos Theater.